U.S. Pat. No. 4,652,700 (the '700 patent) discloses a communication system having a centralized storage. As shown in the '700 patent, voice communications may be stored in the centralized storage means, which voice communications are subsequently transmitted to specifically predetermined terminal stations. In this regard, such a function called "future delivery" which utilizes a communication system having a centralized storage is already known in the prior art from a publication by VMX, Inc., of the U.S., namely the "VMX User's Guide." In accordance with this "future delivery" function, a telephone subscriber, for example, subscriber A, can store a communication in the centralized storage of the communication system, which communication is intended for delivery to another telephone subscriber, for example, subscriber B. Further, in accordance with this "future delivery" function, the communication is delivered to subscriber B at a later or future point in time. The function of transmitting the communication at a future point in time can result in substantial costs. This is especially true whenever the communication from the centralized storage of the communication system takes place via the public switched network to terminal stations which are far from the communication system.
German Patent Disclosure DE 33 30 376 A1 and European Patent Application EP 0 380 190, disclose a method for storing call data generated during call charging at telephone exchanges and, especially private branch exchanges, as well as a procedure called "automatic generation of billing records." These prior art methods serve to record charges for telephone connections that are initiated by users of respective telephone exchanges.
U.S. Pat. No. 3,867,582 discloses a configuration of private branch exchanges known as "remote control for private automatic branch exchanges." As disclosed in this patent, external terminals can avail themselves of services offered by the private branch exchanges as if they were internal terminals. As a consequence of this, costs are reduced for external terminals, which costs would occur in conjunction with connection which would otherwise be set up by interconnecting an exchange (operator) or by using credit cards.
U.S. Pat. No. 3,728,486 discloses a "voicegram service" wherein a central exchange, a voicegram service center, initiates recording of voice messages from a send-side station; transmits voice messages to a receive-side station at a predetermined time; and bills the charges for this service to the send-side station.
Despite the above-described services which are available in the art such as, for example, "future delivery" of communications; storing call charging data at telephone exchanges such as private business exchanges; remote control; and voicegram, there is a need in the art for a method which provides users of telecommunication terminal stations which are external to a private business exchange the ability to utilize the capabilities of such private branch exchanges.